JPS6237572A - Shaft seal device - Google Patents

Abstract

PURPOSE:To eliminate the need of a device special for increasing the pressure of sealed liquid by providing plane sliding surface opposite to each other, disposing a spiral groove except the vicinity of the inner and outer peripheries on one of the sliding surfaces, and disposing an annular groove to which the low pressure side of the spiral groove is connected on one of the sliding surfaces. CONSTITUTION:When a rotary shaft 3 is rotated, a spiral groove 9b draws in a liquid from the open end on the center side by pumping action, so that dynamic pressure is generated toward the outer periphery to increase pressure, and at the terminal end portion of the spiral groove 9b, pressure a little higher than the pressure of a sealed fluid in a space H is generated. A liquid film is formed between sealing surfaces 11, 21, so that fluid lubrication is conducted between both sealing surfaces 11, 21. A flat portion 16 and the end surface of a rotary ring 1 work as end surface seals on the inside diameter side of the sealing surfaces 11, 21, whereby a sealed liquid supplied to the sealing surfaces 11, 21 is prevented from leaking to the space A on the atmosphere side.

Description

[Detailed Description of the Invention] [Objective of the Invention] "Industrial Application Field" The present invention is a shaft sealing device for a rotating shaft, in particular, an end face seal such as a mechanical seal, and a sealing device for sealing a rotary shaft such as a toxic or flammable gas or liquid. This invention relates to a shaft sealing device for fluid that must never leak.

"Prior Art" An example of a conventional device of this type is shown in FIG. 5, which is a longitudinal sectional view. In the figure, a space H inside the casing 1 is sealed with a high-pressure sealing fluid, and A is a space with the atmosphere on the outside of the casing, and the sealing fluid in the space H flows out to the atmosphere side space A. The sealing surface /l of the rotating ring / integrated or fixed on the rotating shaft 3 and the sealing surface 2 / of the stationary ring are designed to slide under fluid lubrication or boundary lubrication. There is.

The stationary ring is pushed in the axial direction by a spring 3 against the casing side, but the casing 4Z1 is locked by a rotation preventing member (not shown) so that it does not rotate. Also, the stationary ring slides on the casing side, and the place where it slides in the axial direction is an O-ring! is provided to separate space H and space R. A floating ring seal 6 is pressed against the end face of a cover /II which is sealed and fixed to the casing and the atmosphere side space A by a spring /3 disposed in the axial direction between the casing 1 and the rotating ring seal 6.

A pressure fluid of p+Δp (Δp is several KP/cm2) relative to the pressure p of the sealing fluid in the space H is supplied to the space through the supply hole 7, and the sealing surfaces of the rotating ring/ and the stationary ring//; 1/, due to the end face seal effect, the pressure difference l of the above Δp prevents the liquid in the space from leaking into the space H, and the sliding surface between the floating ring seal 6 and the rotating shaft 3 prevents the liquid in the space from leaking. Leakage of liquid into the atmosphere side space A is suppressed.

``Problems to be Solved by the Invention'' This device requires: (1) When sealing high-pressure fluid, a special supply device is required to increase the pressure of the liquid to be sealed. ■It is necessary to always control the differential pressure between the sealing fluid and the liquid that confines it. ■E because it is a contact type seal
If the sealing conditions are strict, reliability will inevitably be lacking and the lifespan will be short. (2) The space is under high pressure, and if the liquid leaks from the seal 6, it becomes atmospheric pressure, resulting in a large loss.

■In order to seal the high-pressure fluid, a shaft sealing means is required to seal the liquid, which has a higher pressure than the high-pressure fluid, from the atmosphere side space, and because of the high pressure, a simple one may not be enough. Therefore, the axial length of the entire shaft sealing device may have to be extremely large. There are other problems.

The present invention solves the above-mentioned problems in a shaft sealing device configured to seal a rotating shaft with an end face seal, and provides a shaft sealing device that is highly reliable, does not require a special pressure booster, and has a short axial length. The purpose is to provide equipment.

[Structure of the invention]

"Means for Solving the Problems" The present invention provides a rotating ring that rotates together with a rotating shaft, and a stationary ring that is attached to a casing. In a shaft sealing device that performs sealing, the opposing sliding surfaces are flat, and a spiral groove is formed, except near the inner and outer peripheries of either sliding surface, to draw in the liquid on the low pressure side toward the high pressure side by the rotation of the rotating ring. established,
A shaft having an annular groove communicating with the low-pressure side of the spiral groove on one of the sliding surfaces, and a passage communicating with the annular groove and a low-pressure liquid supply source for sealing the sealing fluid via a stationary ring. It is a sealing device.

``Function'' Low-pressure liquid is fed from a low-pressure liquid supply source through a passage including a supply hole in the stationary ring to an annular groove communicating with the low-pressure side of the spiral groove, and when the rotating shaft rotates, the rotating ring As it rotates, due to the effect of the spiral groove, the liquid on the low pressure side moves to the high pressure side where the spiral groove stops, increasing the pressure and generating dynamic pressure. This pressurized liquid seals the sealing fluid on the opposing flat surface of the sliding surface on the high pressure side. On the low-pressure side, shaft sealing with the atmospheric side is performed on the opposing flat surface of the sliding surface.

"Example" Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view. Similar to the conventional example shown in Fig. 5, a high pressure sealing fluid is sealed in the space H inside the casing.
A is the atmosphere side space on the outside side of the casing. Although the sealed liquid is supplied from the space, the pressure may be equal to or lower than the pressure of the sealing fluid in the space, and may be equal to atmospheric pressure.

Sealing surface of a rotating ring integrally or fixed to the rotating shaft 3
/ and the sealing surface 21 of the stationary ringco are sliding surfaces that slide through the liquid film. A spring is disposed in the axial direction between the stationary ring and the casing side, and the stationary ring is pushed in the axial direction by the spring 5 toward the rotating ring, or is rotated by being locked on the casing side with a rotation stopper (not shown). It is designed not to. Further, an O-ring t is provided in parallel to the cylindrical portion where the stationary ring is slidably fitted to the casing side.

The sealing surface of the stationary ringco, 21, has a flat top ya and a spiral groove, as shown in FIG. 2 of the front view. It consists of spiral grooves t in which grooves t are alternately lined up, and flat portions 10 located on the inner and outer sides of the spiral grooves t and on the inner and outer peripheries on the same plane as the apex ya. Each spiral groove tb is connected to the center by an annular groove /3. An annular groove 15 and an 0 ring for the stationary ring! A supply hole 7 is provided which communicates with the circumferential groove provided in the stationary ring between , and the supply hole 7 communicates with the circumferential groove . The supply hole 7 communicates with a source of encapsulating liquid provided in the space.

The rotating direction of the rotating shaft 3 is counterclockwise in FIG. 2, and a spiral groove is formed due to the pumping action. In 1), liquid is drawn in from the open end on the center side, dynamic pressure is generated toward the outer periphery, and the pressure increases, and at the end (outermost periphery) of the spiral groove 9b, the pressure is slightly higher than the pressure of the sealing fluid in space H. Pressure is generated, and a liquid film is formed between the sealed surfaces // and 2, providing fluid lubrication between the two sealing surfaces.

The maximum pressure of this fluid lubrication liquid film is set so that the sealing fluid in the space H does not enter, or a small amount of liquid on the space side leaks to the space H side. This is particularly effective when the sealing fluid on the space H side is harmful, or even if it is not harmful in itself, it will cause serious problems if it leaks.

If the load on the sealing surface //, 2/ is W, and the pressure at the end of the spiral groove 9b is T'g, then the sealing surface //, -2/ is completely sealed.
If a fluid film is formed at /, W = a p ・
...■ becomes. a is a coefficient determined by the shape of the spiral groove 9b, the number of grooves, the groove depth, etc. On the other hand, the pressing load W of the sealing surfaces // and ko/ is determined by the sealing pressure p and the spring load F of the spring j, so that W=S-p-(-F...C.S is the sealing of the space H The area of the pressing part of the stationary ring against the rotating ring due to the pressure of the fluid is π(rl2-rl
However, the outer diameter of r2-sealing surface //, 2/ is 1.2r.
+ - diameter of the sliding portion of the stationary ring and the casing. From formulas (■) and (■), apg=S−p10F.

If S is determined so that S = a = k, then F
'=k(p -p), and the flat part 10 of the sealing surface
The differential pressure p = (p, 6 - p) at is always constant regardless of the sealing pressure if the spring load is determined. Further, the groove shape and groove depth of the spiral groove vb are determined so that the thickness of the fluid film on the sealing surfaces //, 2/ is as thin as possible. Therefore, the sealing surface //.

In 2/, due to the pumping action of the spiral groove yb, the pressure of the sealing fluid is constantly raised to a high pressure by ΔP (several kff/cm), thereby sealing the sealing fluid and minimizing the gap between the sealing surfaces // and λ/. The value of Δp is determined only by the magnitude of the spring load of the spring 5, and does not depend on the rotational speed, sealing pressure, or type of sealed liquid.

The sealed liquid supplied to the sealing surface //, λ/ is the sealing surface //,
On the inner diameter side of 2/, the flat portion /A and the end face of the rotating ring / act as an end face seal to prevent the sealed liquid from leaking into the atmosphere side space A.

The liquid sealed in the sealing surface //, 2/ from the supply hole 7 through the circumferential groove /7, the supply hole /za, and the annular groove /3 may be oil, water, etc. if the sealing fluid is a gas. If it is a liquid, choose another safe cleaning liquid. In particular, in the latter case, it is desirable to seal the liquid containing foreign matter with a clean liquid of the same kind. In addition, the sealed liquid sent from the space side leaking to the space H side where the sealed fluid is located can be easily separated if the sealed fluid in the space H is a gas, which is highly effective; It is very effective if you don't mind.

The liquid sealed from the space may be at atmospheric pressure,
It may be supplied by a low head pump or, if the pump uses this sealing device, the liquid itself may be introduced at low pressure on the suction side of the pump. Therefore, the flat portion /6 serving as the end face sealing portion only needs to have a sealing ability between the opposing surfaces to prevent the low pressure liquid from leaking into the atmosphere side space A. Although the spiral groove qb or the annular groove /j was on the stationary ring side, it may also be on the rotating ring side. In this embodiment, the depth of the spiral groove 9b is 3 to SO μm, and the thickness of the liquid film on the sliding surface is about 1 to 3 Am.

FIG. 3 is a longitudinal sectional view of another embodiment of the invention. While the flow in the spiral groove portion 9 in the first embodiment is an outward flow, in the embodiment shown in FIG. 3, the flow is an inward flow.

A sealing fluid exists in the space (2), a liquid for sealing the sealing fluid exists in the space (2), and an atmosphere exists in the space (Aζ).

The attachment relationship of the stationary linkage to the casing l and the relationship of the rotating ring to the rotating shaft 31 are the same as in the previous embodiment.

FIG. 3 is a front view of the stationary link shown in FIG. 3. A flat portion 10 is provided on the inner and outer circumferential sides of the stationary link. /A is the side where the flat portion 10 slides on the end face of the rotating ring / via a liquid film to seal the sealing fluid in the space H. The outer peripheral side of each spiral groove 91) is an annular groove /! The annular groove 15 and the annular groove /7 on the outer periphery of the stationary linkage communicate with each other through the supply hole /l. /q is a plug required for drilling the supply hole.

When the rotating shaft 3 rotates in the clockwise direction f in FIG. This pressure seals the surface //.

On the center side of -/, the pressure becomes slightly higher than the pressure of the sealing fluid in the space H by ζ, and sealing is performed.

Is there a spiral groove in the third embodiment? The depth of b varies depending on the viscosity of the sealed liquid, for example, in order to generate sufficient dynamic pressure and form a fluid film as thin as possible, but it is 3 ~! The size is set to r011m. The thickness of the liquid film between the sliding surfaces is approximately 3 μm.

The material of the rotating ring/stationary link in each embodiment is a hard material, especially ceramics (preferably silicon carbide SiO or silicon nitride Si3N4) on the side where the spiral groove is provided.
The mating sliding member is preferably made of alumina ceramics, cemented carbide, stainless steel, high lead bronze, ordinary cast iron, carbon, or the same material as the side on which the spiral groove 9b is provided. The sliding surfaces of the rotating ring and the stationary link are mirror-finished, and the sliding is caused by complete fluid friction due to the dynamic pressure effect of the spiral groove. According to experiments, the coefficient of friction is extremely low at 0.003, making it easy to cool. There's almost no need. In addition, the part provided with the spiral groove may be bonded to a stationary link or a rotating ring, with the member provided with the spiral groove in the form of a thin disc as described above, and if this mating member is also made of ceramics, it may be a plate in the same way. It may also be glued together.

In a shaft sealing device in which the sliding surfaces of the respective end faces of the stationary ring attached to the singe side are pressed and slid, and the sliding surfaces form a seal, the opposing sliding surfaces are flat, and either sliding surface is sealed. A spiral groove is provided except near the inner and outer peripheries of the sliding surface to draw the liquid on the low pressure side toward the high pressure side by the rotation of the rotating ring, and an annular groove is provided on one of the sliding surfaces to communicate the low pressure side of the spiral groove, Since the shaft sealing device has a passage that communicates the annular groove with a low-pressure liquid supply source for sealing the sealing fluid via a stationary ring, ■ there is no need for a special supply device to boost the pressure of the sealed liquid. .

■ No device is required to control the pressure difference between the sealed liquid and the sealed fluid.

■ 'The sealing surface is non-contact, so it is highly reliable.
It has a long lifespan.

■ No special sealing means is required to seal the sealed liquid, and leakage can be extremely reduced. Furthermore, since the sealing means are not arranged in parallel in the axial direction, the length of the shaft sealing device can be reduced.

The following effects occurred.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 1 is a front view of the stationary ring of FIG. 7, and FIG. 3 is a longitudinal sectional view of another embodiment.
FIG. 5 is a front view of the stationary ring shown in FIG. 3, and FIG. 5 is a longitudinal sectional view of the conventional example. /... Rotating ring Co... Stationary ring 3... Rotating shaft
D...Casing J...Spring 6...Floating ring seal Ri...Supply hole Z...O-ring 9...
Spiral groove 9I! L...Top 9b...Spiral groove 10...Flat part //...Sealing surface /3...
Spring / G... Cover / S... Annular groove / 4... Flat part / 7... Circumferential groove / To... Supply hole /?・Bung,
, 2/... Sealing surface A, 'H, T,... Space. Patent applicant Ebara Research Institute, Inc. Ebara Corporation

Claims (1)

[Claims] 1. In a shaft sealing device in which a rotating ring that rotates with the rotating shaft and a stationary ring attached to the casing side are pressed against each other by sliding surfaces on their respective end faces, and sealing is achieved by the sliding surfaces, the rotating ring and the stationary ring are opposed to each other. The sliding surface is flat, and a spiral groove is provided on either sliding surface, except near the inner and outer peripheries, to draw the liquid on the low pressure side toward the high pressure side by the rotation of the rotating ring. A shaft sealing device that is provided with an annular groove that communicates with the low pressure side of the shaft, and a passage that communicates between the annular groove and a low-pressure liquid supply source for sealing the sealing fluid via a stationary ring.